1. Field of the Invention
This invention relates to a semiconductor device and its manufacturing method specifically to a packaging technology of a semiconductor chip.
2. Description of the Related Art
An MCM (Multi-Chip Module) has received attention in recent years as a new packaging technology. The MCM is a high performance module implemented by incorporating a plurality of semiconductor chips into a single package. There are various kinds of MCMs depending on how the semiconductor chips are placed. Among them, attention is focused on a “stacked MCM” which is made by stacking a plurality of semiconductor chips.
An example of the stacked MCM structure is shown in FIG. 14. The stacked MCM 200 is made by stacking a plurality of semiconductor chips 204. Via holes 205 cutting through the semiconductor chips 204 are formed by laser processing. Barrier metals 202 are formed on side surfaces of the via holes by sputtering or by CVD (Chemical Vapor Deposition). Vertically adjacent semiconductor chips 204 are connected with each other through wirings formed by burying conductive material in the via holes 205 by copper plating.
Insulation between the semiconductor chips 204 is maintained by inserting a thermoplastic film 203. The plurality of semiconductor chips 204 are stacked by repeating such manufacturing process steps. Connections to an external circuit are made through conductive terminals 206 attached to a semiconductor chip 204 disposed at the bottom of the stack.
The stacked MCM 200 is manufactured by the manufacturing steps described above. The stacked MCM mentioned above is disclosed, for example, in Japanese Patent Application Publication No. 9-232503.
Manufacturing the stacked MCM 200 described above requires forming via holes which are tens of micrometers in diameter and in depth and burying the conductive material in the via holes. Consequently the manufacturing process requires expensive apparatus not used in conventional packaging of semiconductors such as a laser processing machine to process the via holes, barrier CVD equipment to form the barrier metal films and copper plating equipment to bury in the via holes, causing a problem of higher manufacturing cost.